Study the structure of X(3872) from its lineshape

Abstract

We fit the invariant mass distribution of ${X(3872)}\rightarrow{J}/{\psi}\pi^+\pi^-$ from LHCb using the propagator for S-wave near-threshold states in effective field theory. In this way, we can directly determine the $Z$ which measures the projection of the bound state on the compact state in ${X(3872)}$. Consequently, the structure of ${X(3872)}$ can be elucidated. Moreover, the fitting result also can describe well the data for ${X(3872)}\rightarrow{D}^{0}\overline{D}^{0*}$ from Belle experiment, which demonstrate the reliability of our fitting. The fitting indicates that $Z$ is a non-vanishing value within error, which supports that $X(3872)$ has a compact short-distant core.